EDIT... again: more searching has turned up this post:
http://coloradok5.com/forums/showpost.php?p=2716910&postcount=15
http://coloradok5.com/forums/showpost.php?p=2716910&postcount=15
CK5
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help me tune my Demon
- Thread starter Chevy305
- Start date
Ok a little more update,
I checked the plugs again and it seams to still be running a hair lean. So I will jet up to a either a 71 or 72 and go from there.
Also in installing new valve covers I re-adjusted the valves. I had one exhaust valve too tight and one too loose. The engine still sounds and performs the same as far as the mid range crackling goes.
I changed to a green accelerator pump cam in the #2 hole and it has significantly helped the hesitation problems. I might still want to bump up to the 50cc pump though to totally eliminate the hesitation.
I will also need to go to a heavier secondary spring as well as there is still a slight flat spot in acceleration.
I didn't get a chance to install the H-pipe but that will come this week.
We're getting there! I appritiate the help thus far
I checked the plugs again and it seams to still be running a hair lean. So I will jet up to a either a 71 or 72 and go from there.
Also in installing new valve covers I re-adjusted the valves. I had one exhaust valve too tight and one too loose. The engine still sounds and performs the same as far as the mid range crackling goes.
I changed to a green accelerator pump cam in the #2 hole and it has significantly helped the hesitation problems. I might still want to bump up to the 50cc pump though to totally eliminate the hesitation.
I will also need to go to a heavier secondary spring as well as there is still a slight flat spot in acceleration.
I didn't get a chance to install the H-pipe but that will come this week.
We're getting there! I appritiate the help thus far
Put the pink cam on before you try a 50 cc pump. Just make sure it still has .015" clearance at WOT. You shouldn't need a 50 cc pump for your setup, but every one is different.
I tried the pink cam in the #2 and its acctually slightly worse than the green cam. Should I try it in the #3 spot? If so which hole do I put the screw through on the carb?
Slapperbar
Retired Navy NDT Examiner
I'm lurkin'.
One thing you have to watch carefully is to make sure that the lever is contacting the cam at idle. Sometimes the lever will be resting on the throttle shaft torsion spring at idle, and not the cam, which will cause a flat spot off idle. Just use whatever combination of holes allows the cam to be the constant contact point. Some people say to bend the lever a little with a crescent wrench (off the carb) to get it to change the angle slightly, but I have never found it necessary, I just rotate the cam until it is conacting the lever, and then use the closest hole combination. The pink cam has 3 holes so it isn't necessary, but in other cams I have drilled a new hole so it can contact the lever at idle.
ok well I installed the 50cc pump. I definately have a much improved responciveness however, it still doesn't respond well to sudden throttle changes, such as mashing the gas or dumping the clutch. Right now I am using the green cam in the #1 hole. Anything bigger is too big but anything smaller is still too small.
I broke down and called Barry Grant tech support. They out right told me that I have the wrong carboretor for my engine. They said a 750 Speed Demon with mechanical secondaries and annular boosters is what I need. I looked up the price and its about $500, which of coarse is about $500 more than I want to spend. I have always been told that for a street/offroad friendly vehicle you want vac secondaries and side hung floats. The speed demon is based off of a Holley 4150 which I have always heard horror stories about offroad. But on the other hand this carb may clear up my tuning problems...
what do you guys think?
I broke down and called Barry Grant tech support. They out right told me that I have the wrong carboretor for my engine. They said a 750 Speed Demon with mechanical secondaries and annular boosters is what I need. I looked up the price and its about $500, which of coarse is about $500 more than I want to spend. I have always been told that for a street/offroad friendly vehicle you want vac secondaries and side hung floats. The speed demon is based off of a Holley 4150 which I have always heard horror stories about offroad. But on the other hand this carb may clear up my tuning problems...
what do you guys think?
*cough*should'veboughtanEdelbrock*cough*
just kidding, should've gone with a q-jet.
OK, seriously now, The mech secondaries in the carb they say will work better, most likely will work better. But you won't like what it does to your mileage.
just kidding, should've gone with a q-jet.OK, seriously now, The mech secondaries in the carb they say will work better, most likely will work better. But you won't like what it does to your mileage.
Ok so I won't be able to afford a new carb for a while now on my current budget. So I want to make what I have work to its best ability. Please offer any suggestions:
Right now I have #71 main jets, a 50cc pump, green cam in the #1, and #35 nossles.
So I still have off idle hesitation, actually its throughout the rpm range anytime I give the engine more throttle. My 1000rpm-2000rpm is very sluggish. 2000rpm and up it pulls real strong after the engine clears its hesitation out from the throttle change. Also since the weather has gotten cooler I have noticed that the engine has to run at opperating temp for a few minutes before the engine starts responding better. Then if I shut it off for a few minutes the engine suddenly runs like it does on a hot summer day. I am thinking this has something to do with heat soak, I am going to remove the carb spacer and see if that makes a difference.
Right now I have #71 main jets, a 50cc pump, green cam in the #1, and #35 nossles.
So I still have off idle hesitation, actually its throughout the rpm range anytime I give the engine more throttle. My 1000rpm-2000rpm is very sluggish. 2000rpm and up it pulls real strong after the engine clears its hesitation out from the throttle change. Also since the weather has gotten cooler I have noticed that the engine has to run at opperating temp for a few minutes before the engine starts responding better. Then if I shut it off for a few minutes the engine suddenly runs like it does on a hot summer day. I am thinking this has something to do with heat soak, I am going to remove the carb spacer and see if that makes a difference.
CherryK5
1/2 ton status
Any way you can get a video of the pop?
And a video of the accelerator while you drive so we can see/hear the hesitation?
And a video of the accelerator while you drive so we can see/hear the hesitation?
Ever get it running right?
Martin
Martin
so if im reading that correctly...
sizing in hole 1 is... white smallest and pink largest??
side note for this chart... on to use hole 1 or 2.. watch this and look at 50 seconds...
http://www.youtube.com/watch?v=eiRIfcrc2yA
since mine pops it is recommended to jet bigger... so i will do that...
watch this and it states.. get the nozzle right first.. then fine tune with pump cam...
http://www.youtube.com/watch?v=w3F3ssOb8lg&feature=related
thanks for asking,
The short answer is no, but I have been able to learn how to drive it so it wont hesitate. It take a little feathering of the throttle and clutch and leaving the choke slighty applied seems to almost eliminate it.
The long answer is that I found out that the throttle shaft is loose and causing a vacuum leak when I change throttle. This must be a factory defect because its been there since I installed the carb new. So this means when I give it gas air leaks past the throttle shaft causing a lean condition that is why I had to tune it to the maximum accelerator pump shot configuation. In doing internet searches I can't seem to find a new base plate for the carb, so I have to get a hold of Demon tech support which is easier said than done. Their hours are worse than banks.
I am thinking though that I would prefer to save up for an aftermarket injection system.
The short answer is no, but I have been able to learn how to drive it so it wont hesitate. It take a little feathering of the throttle and clutch and leaving the choke slighty applied seems to almost eliminate it.
The long answer is that I found out that the throttle shaft is loose and causing a vacuum leak when I change throttle. This must be a factory defect because its been there since I installed the carb new. So this means when I give it gas air leaks past the throttle shaft causing a lean condition that is why I had to tune it to the maximum accelerator pump shot configuation. In doing internet searches I can't seem to find a new base plate for the carb, so I have to get a hold of Demon tech support which is easier said than done. Their hours are worse than banks.
I am thinking though that I would prefer to save up for an aftermarket injection system.
I have confirmed that this table is correct in my own "seat of the pants" testing. Just start trying combinations and go from there.
Ya if you get a lean backfire then definately increase the pump nozzle size.
yeah i went from a .28 to a .35 now i get a flamethrower out the carb!!!!!!!!
so im hoping a .31 will do...
Why not just go with a GM TBI system? Cheap, and tunable.
As for the carb selection, manual transmission = mechanical secondaries.
Martin
As for the carb selection, manual transmission = mechanical secondaries.
Martin
smalltruckbigcid
1/2 ton status
Good luck Barry Grant went out of business
From Barry Grant
As of today, February 18, 2011 we are ceasing operations at our Dahlonega location and all subsidiary locations. Working with all of you has been the experience of a lifetime. I will value your support as friends, customers, vendors, and media contacts forever. The economic situation has put the company in the position of not being able to find working capital needed to continue operations and get a chapter 11 reorganization plan through the court. In addition to this, is that all of our equipment has been breaking down causing production delays and further hurting cash flow. Reluctantly now we must convert to chapter 7 liquidation after 26 years of business. The [COLOR=green ! important][FONT=inherit ! important][COLOR=green ! important][FONT=inherit ! important]financial[/FONT][/FONT][/COLOR][/COLOR] collapse has closed, or has caused severe restructuring of many companies in our industry. Many individuals have lost everything. We have even lost our home. This is the most humbling experience of my life, and I have no future plans at this point. Thank You for Your Many Years of Support.
That definitely sounds like a lean condition. Feathering gives more pump shots, and the choke makes it more rich. It seems odd the throttle shafts would be bad and ONLY cause a leak when you change the throttle. I would think if there were bad, they would be bad all of the time. I could see how the would shift around in the bore but there would always be slop on one "side" of the circle.
On a side note, I have been eyeing that FAST EFI since they came out with it a couple years ago, and I just bought it a couple weeks ago. I have it mostly installed but still need to finish the fuel system and new exhaust I am doing at the same time. FYI, the FAST throttle body has press in needle bearings on all 4 throttle shaft corners! Check the last page of my build thread for some teaser pics...
